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bh=9bVcYyAmNQfF4Oyy4yApCgMyxztzFQv5/kHOxY7QRho=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=J7cKanBnmSw7efZUH2ZUOOBpWOmVeEL2rxypmpb6+8ZLaoyUJGvSY1VQg0vG68Gsj zy/OSZr5mCeiwjE2zvXgWA8Ahfq52t0k/0oYmPpUMq30X6xQmmw8sTD3A+GLY8jwmc 3c8xxriC2AtTyI8U0jCHasvRTf3R/mBTZuuiWFMP2nCw3dJ0ch3vOHbsxP6xB98oZP HEZokEKW3bSYYEq88XhiElMmiEGIG+VDFxBQipfWZJcOSeMmZoxdiGsrhI1lQW/wpM 5KZJNlkr828mAn6YW5opjYHm7O9dgMUHI8+XAgTognOh28jCe5ycE+667VWtElIsOu t2EoASduivrlA== Date: Mon, 16 Jan 2023 11:00:48 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, david@redhat.com, quic_charante@quicinc.com, lizhe.67@bytedance.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v3] mm/page_ext: Do not allocate space for page_ext->flags if not needed Message-ID: References: <20230113154253.92480-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230113154253.92480-1-pasha.tatashin@soleen.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 9AC951A0010 X-Rspam-User: X-Stat-Signature: hd4xhbcgwt4dms56i1d9twug6bwjdwfx X-HE-Tag: 1673859664-757889 X-HE-Meta: U2FsdGVkX1+GU7o5Nqes0dZAp5NIK3l2cUySU6wnVWOvqPi1dTd+bU9LiPcADeHdRoZTYudigRtWu9V1Q9ZpIaBPmDcUSLYHV1bUcVe931wm6jE9lnm3/Zi6g71tOmNmU3EKOR6mSDPn0cExTV+/5GLOdNgd05rEgE7LjJBAi5SKQJW1RKmCpCbRxJw2Q16z9BgHpF6tv0+dXClH/6pUfaD8sLwVxdZaMPBz+s1gUacwBYmsal+iObAAvE6SmfrFt5UpnuhIC/M8w9Or85JwRzG1pO5k8rwZNwI6Y0EnXC6rwg7MlfaX2KWdS93hJwPCLh5lLAXmYd+NlnLwddieiNioOuSVMIpYSeS/kqq+7aJs31r9rr1b2NYsqUh5qj/C4Aw3udLuRZnFgjO0y21CeMmztkp1lOb2Lpa5deO2Yio56ogZ3rDx874/9GnpYOML38DweH2G4hySAKuPa4sqq8cJQXx6BoPstLt2J6VEkMHuMZtmlaZ9aUEar04pErUPQRHFgUuyzypPoNbHiQcczjSIRwGNrcJzLP7MEXAM9iaYFxEGvI0ELlZns6ZXy7jLtAWrlXchmzyU0hz2bi+sEbQUvvbosolNHF1ecFe1zTdU0k++22/5YHQucyLDoFoh2p6zYtdIemQ1YHEb8LgXtVbqZW8UVW+fdigM+tkewbw685hECHFnBrYBK97F/cf83Sq74/InPQNK8MdygM713YUqRNbRQmx+BH6cUPq4IPAVtoIzAceicQ8TwzDw5kX/gcIcsIhyPfYgXC9Myrjd7r5RGL+1CnlJmyyUtJdLfuwrLqnm0iuHrBL/jYU85K0WEwfwRfYE8RKqugRmRbOQ8xveVVfLVykE+FqTo0pRhXLZoMAnjqYPXBFgkiktN7mWqVwapUKFvJ/Tq0IKhmiwDIGYNC6Qe+7EM9a78HB7g6uUCJtLVXrcoWC76psxudLGlbP4P0OktOLI9rmoG44 nMlraUZU Pqiv1+rKpNOGQFfvAsvnNwbXD1tZwMid1WRtNY0gzgGupCJuer0al+QTNJAT4JHMxVsf/Go7csSSUfVI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jan 13, 2023 at 03:42:53PM +0000, Pasha Tatashin wrote: > There is 8 byte page_ext->flags field allocated per page whenever > CONFIG_PAGE_EXTENSION is enabled. However, not every user of page_ext > uses flags. Therefore, check whether flags is needed at least by one > user and if so allocate space for it. > > For example when page_table_check is enabled, on a machine with 128G > of memory before the fix: > > [ 2.244288] allocated 536870912 bytes of page_ext > after the fix: > [ 2.160154] allocated 268435456 bytes of page_ext > > Also, add a comment before page_ext_operations that describes the > field, and remove check if need() is set, as that is now a required Nit: fields > field. > > Signed-off-by: Pasha Tatashin > --- > include/linux/page_ext.h | 19 +++++++++++++++++++ > mm/page_ext.c | 14 ++++++++++++-- > mm/page_owner.c | 1 + > mm/page_table_check.c | 1 + > 4 files changed, 33 insertions(+), 2 deletions(-) > > Changelog: > v2: Fixed field name in page_owner.c that caused build error. > v3: Added comment before page_ext_operations, removed check if > need is null. > > diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h > index 22be4582faae..be0b465c7d78 100644 > --- a/include/linux/page_ext.h > +++ b/include/linux/page_ext.h > @@ -7,15 +7,31 @@ > #include > > struct pglist_data; > + > +/* Please make it kerneldoc. > + * Each Page Extension client must define page_ext_operations in > + * page_ext_ops array. > + * offset offset to the client's data within page_ext. Offset is returned to > + * the client by page_ext_init. > + * size the size of the client data within page_ext. > + * need() function that returns true if client requires page_ext > + * init() (optional) called to initialize client once page_exts are allocated. > + * using_shared_ext_flags true when client is using shared page_ext->flags > + * field. > + */ > struct page_ext_operations { > size_t offset; > size_t size; > bool (*need)(void); > void (*init)(void); > + bool using_shared_ext_flags; I'd s/using_shared_ext_flags/need_shared_flags. > }; > > #ifdef CONFIG_PAGE_EXTENSION > > +/* > + * The page_ext_flags users must set using_shared_ext_flags to true. > + */ > enum page_ext_flags { > PAGE_EXT_OWNER, > PAGE_EXT_OWNER_ALLOCATED, > @@ -31,6 +47,9 @@ enum page_ext_flags { > * page_ext helps us add more information about the page. > * All page_ext are allocated at boot or memory hotplug event, > * then the page_ext for pfn always exists. > + * Note: that if none of the users of page_ext is setting I'd drop that ^that > + * using_shared_ext_flags to true, the field cannot be used, > + * as it will be overlapped with another data. > */ > struct page_ext { > unsigned long flags; > diff --git a/mm/page_ext.c b/mm/page_ext.c > index 4ee522fd381c..d14dbd44fa49 100644 > --- a/mm/page_ext.c > +++ b/mm/page_ext.c > @@ -71,6 +71,7 @@ static bool need_page_idle(void) > } > static struct page_ext_operations page_idle_ops __initdata = { > .need = need_page_idle, > + .using_shared_ext_flags = true, > }; > #endif > > @@ -86,7 +87,7 @@ static struct page_ext_operations *page_ext_ops[] __initdata = { > #endif > }; > > -unsigned long page_ext_size = sizeof(struct page_ext); > +unsigned long page_ext_size; > > static unsigned long total_usage; > static struct page_ext *lookup_page_ext(const struct page *page); > @@ -106,7 +107,16 @@ static bool __init invoke_need_callbacks(void) > bool need = false; > > for (i = 0; i < entries; i++) { > - if (page_ext_ops[i]->need && page_ext_ops[i]->need()) { > + if (page_ext_ops[i]->need()) { > + if (page_ext_ops[i]->using_shared_ext_flags) { > + page_ext_size = sizeof(struct page_ext); > + break; > + } > + } > + } > + > + for (i = 0; i < entries; i++) { > + if (page_ext_ops[i]->need()) { > page_ext_ops[i]->offset = page_ext_size; > page_ext_size += page_ext_ops[i]->size; > need = true; > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 2d27f532df4c..1a62ab3fc00e 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -99,6 +99,7 @@ struct page_ext_operations page_owner_ops = { > .size = sizeof(struct page_owner), > .need = need_page_owner, > .init = init_page_owner, > + .using_shared_ext_flags = true, > }; > > static inline struct page_owner *get_page_owner(struct page_ext *page_ext) > diff --git a/mm/page_table_check.c b/mm/page_table_check.c > index 93e633c1d587..74cfe89d5f53 100644 > --- a/mm/page_table_check.c > +++ b/mm/page_table_check.c > @@ -45,6 +45,7 @@ struct page_ext_operations page_table_check_ops = { > .size = sizeof(struct page_table_check), > .need = need_page_table_check, > .init = init_page_table_check, > + .using_shared_ext_flags = false, > }; > > static struct page_table_check *get_page_table_check(struct page_ext *page_ext) > -- > 2.39.0.314.g84b9a713c41-goog > > -- Sincerely yours, Mike.